1. Field of the Invention
The present invention relates to an electronic toll collection (ETC) system and a communication method for electronic toll collection, which enable the performance of accounting processing through communication with a system mounted on a vehicle that passes a predetermined communication area of a road.
2. Description of the Related Art
Recently, an electronic toll collection (ETC) system has gradually been increased at tollbooths of toll roads such as expressways. To collect a toll at a tollbooth, an on-road system is installed, while an on-vehicle unit is mounted on a user's vehicle, whereby performing radio communication between the on-road system and the on-vehicle unit. Through the radio communication, the processing for collecting a toll, such as withdrawing a toll from a user's account,previously registered, is automatically executed for the payment of the toll. This way of radio communication eliminates the necessity of stopping users' vehicles at tollbooths for toll payment, thus reducing traffic jams at or near tollbooths and reducing management cost by for example making tollbooths unmanned.
By the way, after such an electronic toll collection system is once introduced and on-vehicle units adapted to the system are supplied to users, there may arise the need for switching over to a system non-adapted to the on-vehicle units that have already been supplied to users. In such a case, replacing the already-equipped user's on-vehicle units with new units is necessary, but the replacement is time-consuming and costly, thus making a quick transition to the new system difficult.
As an example, the above situation may occur when a system employing a different communication protocol (or, simply “protocol”) from the previous one is introduced. One solution to such a case is to install a plurality of types of on-road systems to be adaptable to a plurality of types of on-vehicle units. In this case, to perform communication with the on-vehicle units on the plurality of types of communication protocols, various types of on-road systems should be installed to cope with the on-vehicle units. However, this redundant system is far from its real installation in terms of both installation places and installation cost.